It's short for web log.

Blogs provide commentary or news on a particular subject such as food, politics, entertainment, sports, or news; some function as a more personal online diary. A typical blog combines text, images, and links to other blogs, web pages, and other media related to its topic.

Whether its teen angst, social activism, or merely a passionate opinion on how much you love/hate that new movie/show/album/restaurant/boss, there's a place to write it down, and there's someone who will read it.



Image from xkcd